1. Field of the Invention
The present invention relates to a mobile terminal. More particularly, the present invention relates to a specific absorption rate reducer method for decreasing the specific absorption rate by decreasing the density of current emitted by an antenna of a mobile terminal through a connection part of a main-body and a sub-body, and a mobile terminal using the same.
2. Description of the Prior Art
Generally, a mobile terminal may be classified as a bar type, flip type, or folder type according to its appearance.
The bar type mobile terminal is configured with a data input/output means and a transmitting/receiving module installed in a main-body housing. However, the bar type mobile terminal has a disadvantage in which unintended operation may occur because of having an exposed keypad as a data input means. The bar type also has a limitation in miniaturizing the mobile terminal because of difficulties in securing a great enough distance between a transmitter and a receiver.
The flip type mobile terminal is configured with a main-body, a flip-part, and a hinge connecting the flip-part to the main-body. The flip type mobile terminal has a data input/output means and a transmitting/receiving module installed in the main-body, and may avoid unintended operation by closing a keypad as a data input means with the flip-part. However, the flip type mobile terminal also has a limitation in miniaturizing the mobile terminal because of difficulties in securing a great enough distance between a transmitter and a receiver.
The folder type mobile terminal is configured with a main-body, a folder, and a hinge connecting the folder to the main-body rotatively. The folder type mobile terminal may avoid unintended operation of a keypad by closing the folder tightly to the main-body in a waiting mode, and a great enough distance between a transmitter and a receiver may be secured by opening the folder in a calling mode. Accordingly, the folder type mobile terminal has advantages in miniaturizing the mobile terminal.
Among the above mobile terminals, the present invention utilizes the folder type mobile terminal shown in FIG. 1. FIG. 1 is a perspective view showing a conventional folder type mobile terminal. Referring to FIG. 1, a main-body 110 and a sub-body 150 of the conventional folder type mobile terminal 100 are rotatively assembled to be folded or unfolded by a hinge (not shown). The folder type mobile terminal 100 generally has an antenna (not shown) installed at the connection part of the main-body 110 and the sub-body 150. As a result, a problem exists in that a strong electric field formed by the antenna spreads through the space between the main-body 110 and the sub-body 150.
FIG. 2 is a view showing an electric field formed by a current generated in a calling mode of the mobile terminal shown in FIG. 1. Referring to FIG. 2, if the folder type mobile terminal 100 operates in a calling mode, a current flows in the direction of the arrows, and an electric field A is formed in the surroundings of the folder type mobile terminal 100 as shown in FIG. 2. This electric field generates electromagnetic waves, which may be absorbed by a caller's head and have a harmful influence on the human body.
Accordingly, regulation of electromagnetic wave radiation becomes tighter worldwide. Specific absorption rate (hereafter referred to as ‘SAR’), a measure indicating the rate of electromagnetic waves absorbed by the human body (especially by the head), is used for a standard of human body protection. Accordingly, apparatus and methods for reducing the SAR are being developed.
For example, a ground contact device using a hinge is used as an apparatus for reducing the SAR.
FIG. 3 is a schematic block diagram of a mobile terminal including a SAR reducer in the prior art. Referring to FIG. 3, the mobile terminal 100a includes a printed circuit board (PCB) 110a installed in a main-body, a liquid crystal display (LCD) module 150a installed in a folder, and a hinge 170a connecting a ground pin GND of the PCB 110a and a ground pin GND of the LCD module 150a. 
The hinge 170a generates a current opposite to the direction of a current generated when the mobile terminal 100a operates in a calling mode. That is, when the folder type mobile terminal 100a operates in a calling mode, if a current flows from the main-body of the mobile terminal 100a to the folder, a current in the opposite direction is induced in the hinge 170a. Accordingly, displacement current at the front side of the mobile terminal 100a (that is, a side contacting the human body) is compensated, and thereby the SAR is decreased.
FIG. 4 is a view showing an electric field formed by a current generated in a calling mode of the mobile terminal having the reducer shown in FIG. 3. Referring to FIG. 4, when the mobile terminal 100a shown in FIG. 3 operates in a calling mode, at the rear side of the mobile terminal 100a (that is, the side opposite to the side contacting with the human body), a current flows from the main-body to the folder in the direction of the arrows, and a first electric field A is formed in the surroundings of the mobile terminal 100a by the current. Additionally, at the front side of the mobile terminal 100a (that is, the side contacting with the human body), a current is induced from the folder to the main-body in the direction of the arrows by the current. That is, at a portion installed with the hinge 170a, a current is induced in the opposite direction to a current flowing at the rear side of the mobile terminal 100a. The current is generated at the front side of the mobile terminal 100a, and a second electric field B is thereby formed in the surroundings of the mobile terminal 100a by the current as shown in FIG. 4.
Because the first electric field A and the second electric field B overlap at the front side of the mobile terminal 100a, the displacement current at the front side of the mobile terminal 100a is compensated, and thereby the SAR is decreased.
However, in the radiation characteristic, the SAR and total radiated power (TRP) have a relationship of complementing each other. Accordingly, if the TRP is increased, then the SAR is increased. Conversely, if the TRP is decreased, then the SAR is decreased. In the case of the communication environment utilizing 3 frequency bands, increasing the TRP in a frequency band is limited, because the effect described above applies to all frequency bands.